Originally, offshore oil and gas wells were completed on platforms resting on the ocean bottom, or were completed on the bottom with surface production facilities installed on such a platform. Oil and gas produced at such platforms were either collected by tankers or by flow lines laid on the bottom. To the extent that underwater work was required, it was performed by divers, by submarines, or by simple manipulations from the surface.
More recently it has become necessary to drill oil and gas wells in water which is too deep or too dangerous for convenient underwater operations by divers or for use of platforms standing on the bottom. It has thus become necessary to devise methods of connecting subsea oil and gas wells at the ocean floor with flow lines, hydraulic control lines and electrical cables extending to the surface without the use of divers or any permanent surface structure adjacent the underwater well. Various devices have been proposed for achieving such underwater conditions, as shown for example in U.S. Pat. Nos. 3,968,838 to Baugh, 4,019,334 to Sinclair, et al, and 4,086,778 to Latham, et al. A better understanding of the problems presented may be obtained by reference to the January 1978 issue of Offshore Services magazine, published by Spearhead Publications Limited, at pages 26 to 51.
In connecting, by remote operation, flow lines, hydraulic lines, and electrical conduits to an underwater production unit, it is essential that the hubs or ends of the lines not be damaged during their descent to the ocean bottom, travel along the ocean floor, and movement onto the production unit for connection thereto. If the hubs become clogged with debris and mud or become marred and damaged, a seal cannot be established between the hub mounted on the production unit and the hub on the terminus of the flow lines, hydraulic lines, and electrical conduits. Thus, where no diver assistance is available, it is necessary to protect the hub with a cover which can be removed by remote operation.